1. Field of the Invention
The present invention relates to a silicon-containing resist underlayer film-forming composition and a patterning process using the same.
2. Description of the Related Art
As LSI progresses toward higher integration and processing speed, miniaturization of a pattern dimension is progressing rapidly. In a lithography technology, in accordance with this miniaturization movement, formation of a fine pattern could be achieved by shifting of a light source to a shorter wavelength and by proper selection of a resist composition to meet this shift. Along this movement, in a resin used in the photoresist composition, a resin having a weak light absorption at the wavelength of exposure is wanted; and thus, in accordance with the shift to an i-beam, a KrF, and an ArF, the resin is shifting to a novolak resin, a polyhydroxy styrene, and a resin having an aliphatic polycyclic skeleton. The recent photoresist composition having a high resolution like this tends to lower an etching resistance thereof; and in accordance with this tendency, etching selectivity under dry etching conditions becomes lower so that precise transfer of a resist pattern to a substrate to be processed is becoming difficult.
In the case that miniaturization is made with the same light source, too, when miniaturization is made without changing film thickness of a photoresist film to be used, namely, when a pattern width is made further narrower, aspect ratio of a photoresist pattern after development becomes so large, resulting in causing a pattern collapse. Because of this, in accordance with progress of miniaturization, thickness of a photoresist film was made thinner so that aspect ratio of the photoresist pattern might fall within a proper range. This movement to a thinner film is also a disadvantageous condition in transfer of a resist pattern to a substrate to be processed under dry etching conditions.
A multilayer resist method is one countermeasure against the problems mentioned above. In this method, an underlayer film having etching selectivity different from that of a photoresist film (namely resist upperlayer film) is intervened between the resist upperlayer film and the substrate to be processed, whereby, after a pattern is formed in the resist upperlayer film, this pattern is transferred to the underlayer film by dry etching by using the upperlayer resist pattern as a dry etching mask, and then further, the pattern is transferred to the substrate to be processed by dry etching by using the underlayer film as a dry etching mask.
A tri-layer resist method is one method of this multilayer resist method, in which a general resist composition used in a monolayer resist method can be used. For example, an organic film comprising a novolak and so on is formed on the substrate to be processed as the organic underlayer film, on it is formed a silicon-containing film as the silicon-containing resist underlayer film, and on it is formed a usual organic photoresist film as the resist upperlayer film. The organic resist upperlayer film has good etching selectivity to the silicon-containing resist underlayer film in dry etching by gas plasma of a fluorine-based gas, so that the resist pattern can be transferred to the silicon-containing resist underlayer film by using dry etching with gas plasma of a fluorine type gas. According to this method, a pattern of a novolak film having a sufficient dry etching resistance for processing can be obtained even if a resist composition with which formation of a pattern having a sufficient film thickness for direct processing of the substrate to be processed is difficult, or a resist composition having an insufficient dry etching resistance for processing of the substrate is used.
Illustrative examples of the silicon-containing resist underlayer film used in the multilayer resist method as mentioned above include a silicon-containing inorganic film formed by CVD, such as a SiO2 film (for example, Patent Document 1) and a SiON film (for example, Patent Document 2), and those formed by a spin-coating method, such as a SOG film (spin-on-glass film) (for example, Patent Document 3) and a crosslinking silsesquioxane film (for example, Patent Document 4).